Three authors of the new report answer our questions about what the dietary recommendations mean for primary-care clinicians.
Shortly after the “Prevention of Cancer” report was made public, we sought out three members of the panel to comment on the findings:
Walter C. Willett, MD, DrPH, is chair of the department of nutrition and Fredrick John Stare Professor of Epidemiology and Nutrition at the Harvard School of Public Health in Boston; he is also professor of medicine at Harvard Medical School. Steven H. Zeisel, MD, PhD, is Kenan Distinguished University Professor of Nutrition and Pediatrics at the University of North Carolina at Chapel Hill. He also directs two nutrition research programs and is director of the university’s Center of Excellence in Children’s Nutrition. Shiriki Kumanyika, PhD, MPH, is associate dean for health promotion and disease prevention and professor of epidemiology at the University of Pennsylvania School of Medicine in Philadelphia; she is also professor of epidemiology at the Children’s Hospital of Philadelphia.
Q: What was the most jarring change since the first report in 1997?
Dr. Willett: The most important change is that being overweight and obese are now at the top of the list as nutrition-related causes of cancer. Also, dietary fat is not on the list as a probable or conclusive cause of cancer.
Dr. Zeisel: In 1997, we never suspected that there was a strong link between obesity, lack of exercise, and cancer.
Dr. Kumanyika: The impression from the first report was that fruits and vegetables could save you from ever getting cancer. In this report, it’s clear that fruits and vegetables are protective against several different types of neoplasms, but there’s not the sense that eating them is the only thing to do.
Q: How should these findings change clinicians’ approach to counseling patients?
Dr. Willett: Pay just as much attention to patients’ being overweight—or even to modest gains in weight before becoming overweight—as you do to smoking or hypertension.
Dr. Kumanyika: The advice to Americans coming from our report and from the cardiovascular literature is to stop eating that big piece of meat covering half your plate. A meal’s foundation should be plant foods like whole grains and vegetables. Meat should be used as more of a garnish, in small amounts to add some key nutrients but not as the anchor point. This will be a hard message to sell, but clinicians should promote this diet as protective against all the major diseases.
Q: Is a good diet the most important step a person can take toward avoiding cancer? Or is it more important for a person who is a smoker, obese, and sedentary to quit smoking first or begin exercising before tackling dietary changes?
Dr. Willett: Smoking cessation would be the top priority, but there’s no reason not to pay attention to food at the same time. Focusing on the positive aspects of food like fruits, vegetables, and whole grains can provide an alternative to smoking and help avoid weight gains after smoking cessation that sometimes lead people back to cigarettes.
Dr. Zeisel: Smoking is the first thing to stop. Good diet and exercise go together, and I would tackle them next.
Dr. Kumanyika: Quit smoking first. The evidence against smoking is very strong and specific and clear, and the environment and policies that encourage smoking cessation have really improved over time.
Q: Which foods would you single out as the most dangerous?
Dr. Willett: Soda and other sugar-sweetened beverages were identified by the panel as a particular problem because of their contribution to weight gain. Of course, these drinks also contribute to diabetes and heart disease. Soda and fruit drinks will become the country’s next major health target after smoking.
Dr. Zeisel: No food in moderation is bad, except perhaps a particular kind of smoked fish (Cantonese-style salted fish). It is the constant pattern of high fat, lots of meat, and excess calories that people should worry about.
Dr. Kumanyika: I wouldn’t single out a food but would point to a harmful pattern of consumption of high-energy-dense foods with no fruits or vegetables. This causes you to gain weight without having any protective foods in your diet.
Q: Which foods are most protective?
Dr. Willett: No specific food, but from surveys, we know that the largest deficit in the American diet is green, leafy vegetables (e.g., spinach, romaine lettuce, collards, and kale). Roughly half of Americans eat virtually none.
Dr. Kumanyika: Moving away from certain types of foods that sort of slide down your throat and give you a lot of calories, and replacing them with high-fiber foods fit together nicely as a protective pattern. If you start adding foods—even protective ones—without reducing others, you will gain weight. The idea is to fill up with the bulkier foods.
Q: The fast-food industry, agriculture, and giant food companies have a huge economic stake in providing/promoting unhealthy food options. Do you see this ever changing?
Dr. Zeisel: I do. Companies are talking about healthy food as having extra value, and they are developing healthier products. People just have to buy these better foods to motivate the companies more.
Dr. Kumanyika: It has to change. No industry can survive if it slowly kills off the population.
Q: How can nurse practitioners and physician assistants use the report’s findings to best counsel their patients?
Dr. Kumanyika: The challenge for clinicians is how to talk to their patients about diet. Health professionals who have tried to make some of these changes themselves likely have anecdotes and personal experiences they can share with patients, which can be pretty persuasive: “Oh, I changed my recipe by substituting this, and it actually works great. The dish tastes the same.” That can be more convincing than the preachy approach.
Ms. Honen Yard is a senior editor for The Clinical Advisor.